This is kind of stupid but for the last year I've had to put air in the left rear tire every 3 or 4 days. For some reason, I had it in my head that the problem was the valve stem. While replacing the air spring, though, I noticed a screw in the tire. I plugged the tire on Sunday evening and it's been holding air fine ever since.
I didn't fully understand how annoying that was until I didn't have to worry about it anymore.
Stupid trailer brake problem seems to be resolved!
Background info: the factory wired 7 blade trailer connector is partially run through the rear BCM, euphemestically called Signal Acquisition/Activation Module by M-B. When a fully LED equipped trailer is connected directly to the truck, nothing works because the amp draw is so low that SAM doesn't see that a trailer is there. To make the 'too smart for it's own good' truck activate the the trailer lights, a load resistor harness has to be plugged in between truck & trailer.
Theoretically, when the truck knows the trailer is back there it will activate trailer brake & marker lights, change shift schedule, send the +12V signal the brake controller plug, change stability control, turn off reverse proximity sensors, etc. For whatever reason, it would not send the signal to the brake controller previously, even when trailer was hooked up and all other factors indicated it knew the trailer was connected.
The SAM was removed for several months and left to completely drain it's RAM. Recently the mind-scrubbed SAM was reinstalled and some functions that were inop before (power hatch opening), were back online.
Today the trailer was hooked straight to the truck, no load resistor, and as expected, no trailer lights & no trailer brakes functioned. Shut it off, installed resistor plug, all trailer lights worked. New Curt brake controller was plugged in to the factory underdash plug. Dang it, still doesn't work. Just for funsies, plugged in older Curt controller and it worked! It showed connection to the trailer, manual override worked, and it lit up when the brakes pedal was applied. Apparently the brake controller signal had been turned off in the past, but the Vulcan mind wipe allowed it to return to normal function.
Next step, call Curt, see if they will exchange this new defect unit for another one.
Well berkeley.
I was getting ready to load the neon on the trailer when the air spring I just replaced literally exploded.
I can't really get in there to fully see what's going on, but it appears that it managed to pop the air bag out from around the clamp. I was able to reach up under there and pull these parts out.
Yikes, hopefully just a defective part and not a sign of a different issue.
In reply to eastsideTim :
It shot off so cleanly I think it has to be defective. I'd try to put it back together, but there's not really a manual for that and I surely don't want to be in the middle of nowhere on the side of the road trying to figure out what to do when it pops off again.
In reply to wae :
Just to clarify, are both rear air springs new-ish Arnott replacements?
I've only seen them leak slowly, which eventually burns up the compressor. Exploding air springs are kinda rare.
And in my continuing trailer brake saga, I spoke to Curt customer service today, and they are probably going to send me a new Spectrum brake controller. Depends on whether or not they accept my eBay screenshot as proof of purchase of a new factory sealed unit.
In reply to FJ40Jim :
Yeah, one of the original units blew open when I started it up for the first time in 3 years and I put a new Arnott unit on there. The other original one split on a pothole a couple weeks ago. I replaced that with a new Arnott unit and that replacement bag is the one that assploded tonight.
That's great news on the brake controller! Pretty irritating that you had two things that weren't working in tandem, though. Is it possible that one problem caused the other?
Does anybody have any suggestion for a fluid to stop leaks in the M-B hydraulic rear liftgate? I can't ask this question on the MB forums 'cause they will point out that only the AeroShell41 synthetic unicorn tears oil is acceptable.
The vehicle uses a reversible electro hydraulic pump to push/pull a small hydraulic ram in the roof that acts on a lever arm on the tailgate. The pump would run but was not lifting the tailgate, especially in cold weather. I rationalized the fluid was low because of years, and then shrinkage due to cold. Sure enough, the fluid was low, so I topped it off w/ Pentosin EHF, which is abbreviation for the cleverly named Electro Hydraulic Fluid. It is not MB spec, but is spec for the very similar hydraulic power top system on late model BMWs.
Now that the system is full, it is working great but I realize its leaking at the ram which is inaccessibly located above the headliner. I will not repair it, it's far too difficult to remove all the lower interior, to then pull down the giant molded headliner and swap out the entire system for $800. Which is why I'm thinking of using some "power steering stop leak" snake oil. One last hail mary before I give up and replace the gas lift struts with the stiffer ones for manual opening gate.
So yeah, if anybody has any direct experience with a fluid that slowed or stopped leakage in a hydraulic system, I'm all ears.
In reply to FJ40Jim :
Nope. Never had it work. Brake fluid in my one RX-7's power steering system slowed but did not stop a leak, and that is the best experience I had with snake oils in hydraulic systems.
Amazingly enough, the ZF power steering that calls for CHF11S works just fine with $6/qt ATF instead of $40/liter Pentosin. Leaks out just as fast, too 
Well, I have the air spring replacement down to a sub 1hr job.
But it isn't raising that corner at all. I can put it in lifted mode and it says it's "raised level" but it's very much not level. I'll have to go over to the shop and get my Xentry laptop and see what it thinks is wrong.
Hi.
My name is Bill and I'm a big dum dum.
I had the arm of the height sensor backwards. For reference, it goes like this:
This past weekend we took the ML350 to Nelson Ledges racetrack and a couple nights at a Lake Erie state park. Ran & towed fine, but on the way home the CEL lit up. It continued to run fine. The outdated 10 year old SnapOn scanner had trouble pulling codes out of it. The scanner could only offer a " Engine code 186400H/1598464 - undocumented code." The power of the Googlez is not showing any exact match. Tomorrow I'll call the stealership to see if he can offer any insight & LMK if I need to bring it in immediately.
In reply to FJ40Jim :
That reminds me... I need to call my dealer to have them look at the check engine light on mine. Again. Again. I think mine is for the O2 sensor heater circuit and it will turn off for a while but after a day or two it's back. With all the exploding airbags, I kind of keep forgetting about that.
FJ40Jim said:Next step, call Curt, see if they will exchange this new defect unit for another one.
Happy to report that the good folks at Curt honored the lifetime warranty on the fancy Spectrum brake controller and sent me a complete new one. It'll be a few days before I can tear apart the under dash & swap it out.
Trucklet still has a CEL on, since June 25-ish. It continues to run fine and get meh fuel economy.
SnapOn scanner cannot read the code, other than a random looking numeric ID. If anybody knows what a code 186400H/1598464 is, please share.
I finally called MB service today with no satisfaction. The advisor couldn't/wouldn't get me any explanation of the code, so I don't know if it's a "drive and ignore" or a "don't drive & have towed in". They're too busy to get it into a service bay for 3weeks. No loaner available, he wanted me to drop it off and leave it until they get around to it.
We'll see if MrsFJ40 wants to follow me 50+ miles to abandon our nicest car for a month.
In reply to FJ40Jim :
Since June? You amateur! Mine's been on since 2017! 
I can't help but think you guys would greatly benefit from putting together a Xentry/DAS/STAR setup that will actually tell you what the heck is going on. Having maintained a facelift w211 using a cheapy Foxwell (which admittedly was pretty good, gave engine codes I could at least look up with Google), now that I have STAR (my e55's previous owner put set together) I haven't touched the Foxwell in a year.
I guess the next step down the rabbit hole for me is putting Vediamo on the STAR laptop...
In reply to Gammaboy :
I've had good luck with Xentry/DAS using an OpenPort 2.0 on the original ECU. Unfortunately, the version that I've, uhm, "acquired" is from before the post-AEM ECUs were included so it doesn't seem to know what to do about talking to the CDI system. I can fiddle with all the other modules. My old MBII was great for pulling codes from the old ECU as well, but even after an update it didn't know about the new ECU so I passed it along. I should look in to getting myself a newer copy.
I do still want to play with Vediamo, though. Even if for nothing more than telling my rear SAM that LED trailer lights are okay.
wae said:In reply to FJ40Jim :
Since June? You amateur! Mine's been on since 2017!
The CEL is how I know the engine is running.
I've been using thinkdiag2 for last few months. On the 211 gasser it disabled EGR, switches fuel maps, timing maps, throttle maps, activated SBC brake hold and a bunch of other options that were unavailable with icarsoft or foxwell. It hasn't been able to code anything significant on the 642 unfortunately.
Today we took the W164 about 300 mi round trip to Parma to pickup a racecar donor. The CEL was on at departure, but went out after 1-2hrs of driving. It was showing 19.5mpg towing the empty trailer, and the trip average was down to 18.8 at the end, which I thought was acceptable.
Pics or it didn't happen:
In reply to FJ40Jim :
I see your tastes in turbocharged European vehicles of dubious reliability extend beyond just Mercedes.
In reply to FJ40Jim :
You were very close to me
There was an xratty in Parma?? Glad I did not know until after you bought it.
In reply to eastsideTim :
Yes, unreliability was one key component to the Xratti. Flimsy was the other ingredient.
So far to improve reliability:
Swap 5.0 roller in for 2.3
Swap Ford EEC to Holley carb
Delete turbo
Swap flimsy T9 to Motorsports T5Z
Swap flimsy multipiece driveshaft to aluminum 1piece
swap tiny front brakes & wheel bearings to Spec E46 knuckles, bearings, brakes
swap flimsy LCAs to tubular frt arms & heims
swap some rear end stuff... Yadda, yadda
We've learned from repeated failures that the way to make a reliable, fast Merkur is remove all the Merkur.
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